Synopsis of the Voles of the Genus Phenacomys. 81 



in the mountains of Alberta, British Columbia, and the western United 

 States south to southern Wyoming, central Idaho, and south central 

 Oregon. 



General characters. Size small ; fur dense and woolly ; general color 

 light gray, somewhat tinged with yellowish; feet nearly white; inter- 

 orbital region of skull narrow and smooth ; ascending branches of pre- 

 maxillae narrow. 



Color. Back grizzled grayish brown, with a yellowish tinge, which is 

 most distinct in spring and summer specimens, the fur every where thickly 

 sprinkled with blackish hairs, which, however, do not form a distinct 

 dark dorsal area ; face with very few blackish hairs, but not yellower than 

 back; belly dirty white; feet silvery whitish; tail sharply bicolor, pure 

 white below, mixed brown and white above ; under fur dark plumbeous, 

 this color showing through irregularly on belly and throat. The young 

 are clearer gray than the adults, but otherwise similar. 



Skull. The skull of Phenacomys orophilus is of medium size, that of the 

 type measuring 23.1 mm. in basilar length and 14.2 mm. in zygomatic 

 breadth. The interorbital constriction is narrow, and the frontal ridges, 

 even in very old skulls, are too slightly developed to form a frontal sulcus ; 

 ascending branches of premaxillaries narrow and scarcely expanded 

 posteriorly ; jugal broadly expanded and mortised into zygomatic process 

 of maxillary. 



Teeth. The enamel pattern shows no distinctive characters as corn- 

 pared with the species of the ungava group. The anterior loop of the 

 front lower molar is unusually variable in form, but in the majority of 

 specimens is similar to that of P. latimanus. 



Measurements. Type specimen: total length, 146; tail vertebrae. 38 ; 

 hind foot, 19; average of eight adults from Bear Tooth Mountains, Mon 

 tana: total length, 146.5; tail vertebrae, 31.8; hind foot, 17.7; average of 

 ten adults from St. Marys Lake, Montana: total length, 141.7 ; tail verte 

 brae, 34.5; hind foot, 17.7; average of three adults from type locality of 

 P. oramontis: total length, 144.6; tail vertebrae, 37.5; hind foot, 19.3. 



Specimens examined. Total number, 56. 



Wyoming: Near Laramie, 1 (type of P. truei) ; Tower Falls, Yellowstone 

 Park, 1. 



Montana: Bear Tooth Mountains, 23; Big Snowy Mountains, 1; Mid- 

 vale, 1 ; St. Marys Lake, 12; Summit, 1. 



Idaho : Salmon River Mountains, 4 ; Sawtooth City, 2. 



Oregon: Blue Mountains (10 miles north of Harney), 1 ; Crater Lake, 

 2 ; Diamond Lake, 1 ; Mount Hood, 1. 



British Columbia: Mount Baker Range, 4 (topotypes of P. orophilus). 



Alberta: Ninety miles north of Jasper House, 1. 



General remarks. Phenacomys orophilus is distinguishable from all other 

 species except P. intermedius by its combination of short tail, gray face, 

 and pale color. From P. intermedius it differs in cranial and dental 

 characters. 



The range of this species is not continuous, but is interrupted wherever 

 the mountains are not high enough to be capped by a Hudsonian area of 



